This application is based on Patent Application No. 2000-216498 filed Jul. 17, 2000 in Japan, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a method for controlling the drive energy of an ink jet print head for ejecting an ink from an ejection opening utilizing growth and collapse of a bubble generated in the ink by driving a heat generating resistor element for performing printing and to the ink jet print apparatus.
2. Description of the Related Art
The ink jet print head forms an ink ejection droplet by a variety of methods and causes the ink to adhere to a printing medium such as print paper thereby performing printing. Above all, an ink jet print head of a type which utilizes thermal energy for generating film boiling in the ink for ejecting the ink can be easily manufactured to have a high-density liquid passage arrangement (ejection opening arrangement) by forming an electrothermal transducer (heat generation element) film-formed on the substrate, electrodes, liquid-path wall, top plate and the like, through semiconductor production processes such as etching, vapor deposition, sputtering and the like. Therefore, a high-density multi-nozzle structure can be easily realized, and the ink jet print head has an outstanding characteristic that a high-resolution, high-quality image can be obtained at high speed.
However, the point to be considered in the ink jet print apparatus is applied energy to each heat generation element of the ink jet print head. When the applied energy to each heat generation element is low, film boiling phenomenon of ink tends to become unstable due to energy shortage which changes ejection speed and direction as well as ejection amount of ink resulting in a dot mis-alignment, diminished dot size, slight touching and other deterioration of print image quality. On the contrary, when the applied energy to the ink jet print head is high, a mechanical stress may be exerted on the electrothermal transducer due to excessive thermal energy, resulting in a change of film quality, generating deteriorated ink ejection as described above which sometimes leads to a damage of the ink jet print head.
Then, in order to apply an appropriate drive energy to the ink jet print head, generally, the ink ejection condition or print condition on the printing medium is observed while changing applied voltage or pulse width to the ink jet print head to measure a threshold voltage or pulse width of ejection of each ink jet print head, and the measured value is multiplied with a margin value K determined by a separate experiment so that an optimum drive condition is set.
Further, this optimum drive condition is of course varied with the shape and construction of the electrothermal transducer, ink type and the like. However, even with an ink jet print head of the same type, the optimum drive condition may be varied with film thickness variation, film thickness distribution and the like in the production process.
Japanese Patent Laid-open Publication No. 6-320732 provides memory means such as an EEPROM at the ink jet print head side in which the previously measured optimum drive condition of the ink jet print head is stored so that the stored data is retrieved to the ink jet print apparatus side to perform optimum ejection drive control for each print head.
However, like the above conventional art, even when the memory means is provided in the ink jet print head and the memory means is stored with the optimum drive condition of the print head, because the optimum drive condition is just one stored at the initial condition, the actual optimum drive condition may change as the ink jet print head is used for an extended time.
This is conjectured as due to the fact that while repeating film boiling phenomena by rapid heating of the ink, the dyestuff component and the like contained in the ink are piled up as a scorch on the electrothermal transducer, the surface film of the electrothermal transducer is corroded by a component (such as a chelating agent) contained in the ink, or a repeated thermal stress is exerted on the electrothermal transducer, so that the structure or film quality of each layer constituting the electrothermal transducer change, resulting in varied resistance or thermal conductivity.
However, since, such a phenomenon does not always occur periodically, but the degree of change is different according to various conditions such as operation environment and operation frequency of the ink jet print apparatus, it is very difficult to take a measure by anticipation. For this purpose, it is considered that the ink jet print apparatus is provided with functions adjustable by the user, however, this is not user-friendly and is not always adjusted by the user.
Accomplished under such circumstances, an object of the present invention is to provide a method for controlling a drive energy of an ink jet print apparatus which is capable of continuously applying an optimum drive energy to a print head over an extended period of time without troublesome operation by the user and provide the ink jet print apparatus.
An aspect of the present invention is a method for controlling the drive energy of an ink jet print apparatus for ejecting ink from an ink jet print head to a printing medium by driving a print element. The method comprises the following five steps. The first step is a step for supplying a plurality of different drive energies successively to the ink jet print head. The second step is a step for monitoring temperature of the ink jet print head according to the supply of each drive energy. The third step is a step for judging a threshold drive energy required for ink ejection of the ink jet print head using a value for the supplied drive energy and a value for the monitored temperature. The fourth step is a step for determining a drive condition for ejecting ink on the basis of the threshold drive energy. And the fifth step is a step for driving the print element on the basis of the determined drive condition.
Further, in another aspect of the present invention, in the fifth step, when the determined drive condition is different from drive condition information stored in the ink jet print head, drive condition information stored in the ink jet print head is updated with the determined drive condition data.
Another aspect of the present invention is a method for controlling the drive energy of an ink jet print apparatus wherein a print element is driven to eject an ink from an ink jet print head to a printing medium for performing printing. The method comprises the following four steps. The first step is a step for supplying a plurality of different drive energies successively to said ink jet print head. The second step is a step for monitoring temperature of said ink jet print head according to the supply of each said drive energy. The third step is a step for determining a drive condition for ejecting ink using a value for said supplied drive energy and a value for said monitored temperature. And the fourth step is a step for driving said print element on the basis of said determined drive condition.
With this construction, since the ink jet print head is provided with the optimum drive energy continuously over the service life of the ink jet print head, it is possible to prevent inferior ink ejection or damage to the head, thereby providing always good image quality.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.